The invention relates to a control system for controlling an adjustment device which is operated by electric motor in a motor vehicle.
Such control systems often comprise an indirect anti-trapping system for detecting a trapping situation between an adjustment element which is moved by the adjustment device in an adjustment movement along an adjustment path, and a vehicle element. Such adjustment elements are embodied, in particular, as a window pane, as a motor vehicle seat or as a motor vehicle door or as a tailgate.
The indirect anti-trapping system comprises an analysis unit with which the adjustment unit of the adjustment element can be analyzed. By means of this analysis of the adjustment movement, the analysis unit can determine whether an obstacle which is trapped between the moved adjustment element and the vehicle element is located in the traveling path of the adjustment element. The vehicle element may be any desired component of the motor vehicle toward which the vehicle element moves during the adjustment movement so that the distance between the vehicle element and the adjustment element becomes smaller.
The analysis of the adjustment movement is usually carried out in this context by means of characteristic parameters of the assigned drive unit which serves as a drive for the adjustment unit of the adjustment element. If said parameters differ from a predefined pattern or if they exceed defined threshold values, the anti-trapping system stops and reverses the adjustment movement of the adjustment element. In contrast to direct anti-trapping systems in which a sensor unit detects the mechanical trapping process of an obstacle, the indirect anti-trapping system detects the trapping process by means of the evaluation of the characteristic parameters of the drive unit.
Such indirect control systems are usually tested after the assembly of the assigned adjustment device in the motor vehicle by virtue of the fact that an obstacle is placed in the traveling path of the adjustment element in order to simulate the case of trapping. If the indirect anti-trapping means is triggered, the control system and the adjustment device are classified free of faults.
However, the known control systems have the disadvantage that only adjustment devices which are mounted without faults in this way and which move with such difficulty that their difficulty of movement causes the indirect anti-trapping system to respond are detected as unsuitable. However, certain mounting faults often also cause faulty mechanical running properties which are not detected by the anti-trapping system. These faulty running properties may occur, for example, as difficulties in movement which are below the response threshold for the anti-trapping system. It is also conceivable for incorrect mounting of the adjustment device to lead to undesired easy movements of the adjustment device.
These mounting faults, together with gradually occurring wear phenomena of the adjustment device, can lead, in particular, to a situation in which the difficulty of movement of the adjustment device increases to such an extent that as a result the anti-trapping system is triggered. This undesired effect often occurs only after a certain period of use of the adjustment device by the end user.